Usually, in my experience, it's required for licensure, and given the propensity of The State to require a license for *everything* these days, it's rarely voluntary.

I forget where it was, possibly here in CD, that there was a story about how a northeastern state shut down a functioning, productive hair-braiding chain by applying cosmetology rules to their business ---

1) All the hair braiders were required to possess cosmetology licenses (requiring substantial initial training in things irrelevant to and not covering hair braiding.

2) Requiring the hair braiding chains to have the special sinks and waste disposal arrangements for all cosmetology shops, because they dye and treat hair.

The chain in question did NONE of those things. They braided hair, and that was IT. Not treatment, not cutting, braiding only and not jack else. But the above requirements put them out of business by substantially raising their cost of operation without any additional benefit of any kind.

And THAT was the actual point of the rules -- to reduce competition with standard hair services...

====

And as far as this "certified Tarot" crap goes, how much you want to bet it's required for a business license in at least parts of Cali?